Great Lakes water temperatures close to average heading into weekend

NORTHERN MICHIGAN — Seasonal visitors to the Great Lakes may be expecting warmer temperatures following a mild winter and calm spring, but that may not be the case, said James Kessler, physical scientist with the NOAA Great Lakes Environmental Research Laboratory.

Kessler, who studies ice coverage, said this winter's seasonal ice coverage average among the Great Lakes was the lowest on record. The annual maximum ice coverage for the season was the fourth lowest recorded as well.

"Ice cover is closely related to lake surface temperature and air surface temperature," Kessler said. "All those things are very closely related. Obviously, the lake surface needs to be cold enough in order to freeze, so if it isn't freezing, that means it's warmer, and the air and then the water temperatures sort of directly influence each other."

While water temperatures did start higher than usual this spring, the summer months have brought the water temperatures back to pretty regular and expected numbers, he said. On Tuesday, for example, water temperatures around the Great Lakes were all close to average.

That said, it's difficult to compare water temperatures without looking at the full season of data, he said. Great Lakes temperatures and water levels can be impacted by the state of the lakes dating back to a year prior.

Lake Superior, for example, holds a thermal memory due to how deep the lake is, meaning temperatures the lake saw a year prior could be impacting the temperature of the lake on that day. For Lake Erie, however, a more shallow lake, it's affected by the past lake conditions less.

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As for water levels, the Great Lakes are continuing to see the typical oscillation they do between seasons.

During the fall going into winter, Kessler said, the lakes typically see lower levels because the cold, dry air contrasting with the warmer lakes will cause a lot of evaporation. Once the water temperatures cool down, however, there's less evaporation. As ice melts in the spring and there are spring storms, water levels start to rise again, seeing more runoff into the lake.

While things like ice coverage, water temperatures and evaporation all contribute to changes in water levels, Kessler said just because there could be a season with a lot of ice coverage does not necessarily mean water levels will be higher.

For more information on water temperatures, visit coastwatch.glerl.noaa.gov/statistics/average-surface-water-temperature-glsea.

— Contact reporter Karly Graham at [email protected]. Follow her on Twitter at @KarlyGrahamJRN.

This article originally appeared on The Petoskey News-Review: Great Lakes water temperatures close to average heading into weekend